Publication

Application

Priority

US 27557701 P 20010314

Abstract (en)

A method for forming an isocyanate-functional prepolymer having a low residual isocyanate content, comprising (a) reacting a polyol selected from the group consisting of polyether polyols, polyester polyols, polyester polyether polyols, acrylic polyols, glycols and mixtures thereof, and isocyanate monomer to form a reaction mixture comprising prepolymer with an NCO content in the range from 2.5 to 11.5% by weight, and an average NCO functionality in the range from 2.0 to 4.0; and (b) passing the reaction mixture comprising prepolymer and unreacted isocyanate through a short-path evaporator to remove unreacted isocyanate to a level of less than 0.15% by weight, is provided. Preferably, the short-path evaporator is operated at a pressure in the range from 0.1 to 10 Pa, and has a condenser temperature in the range from 25 to 75 DEG C.